title: Homocysteine restricts copper availability leading to suppression of cytochrome C oxidase activity in phenylephrine-treated cardiomyocytes.
abstract: Cardiomyocyte hypertrophy induced by phenylephrine (PE) is accompanied by suppression of cytochrome c oxidase (CCO) activity, and copper (Cu) supplementation restores CCO activity and reverses the hypertrophy. The present study was aimed to understand the mechanism of PE-induced decrease in CCO activity. Primary cultures of neonatal rat cardiomyocytes were treated with PE at a final concentration of l00 µM in cultures for 72 h to induce cell hypertrophy. The CCO activity was determined by enzymatic assay and changes in CCO subunit COX-IV as well as copper chaperones for CCO (COX17, SCO2, and COX11) were determined by Western blotting. PE treatment increased both intracellular and extracellular homocysteine concentrations and decreased intracellular Cu concentrations. Studies in vitro found that homocysteine and Cu form complexes. Inhibition of the intracellular homocysteine synthesis in the PE-treated cardiomyocytes prevented the increase in the extracellular homocysteine concentration, retained the intracellular Cu concentration, and preserved the CCO activity. PE treatment decreased protein concentrations of the COX-IV, and the Cu chaperones COX17, COX11, and SCO2. These PE effects were prevented by either inhibition of the intracellular homocysteine synthesis or Cu supplementation. Therefore, PE-induced elevation of homocysteine restricts Cu availability through its interaction with Cu and suppression of Cu chaperones, leading to the decrease in CCO enzyme activity.
authors.affiliation: Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Zuo
authors.forename: Daoyin
authors.initials: D
authors.lastname: Dong
authors.forename: Miao
authors.initials: M
authors.lastname: Sun
authors.forename: Huiqi
authors.initials: H
authors.lastname: Xie
authors.forename: Y James
authors.initials: YJ
authors.lastname: Kang
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001667:Binding, Competitive / Q000187:drug effects; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D003300:Copper / Q000378:metabolism*; D000079922:Copper Transport Proteins; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006710:Homocysteine / Q000378:metabolism*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: C585959:COX11 protein, rat; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; C491004:Cox17 protein, rat; D024101:Mitochondrial Proteins; D006710:Homocysteine; D010656:Phenylephrine; D003300:Copper; D003576:Electron Transport Complex IV